1. Field of the Invention
The present invention relates to an anti-slip control device for controlling drive wheels of a motor vehicle during acceleration of the vehicle, particularly upon starting of the vehicle, so as to prevent an excessive amount of slip of the drive wheels.
2. Discussion of the Prior Art
In the case where a drive torque of a drive wheel of a motor vehicle during acceleration of the vehicle is excessively large in relation to a friction coefficient of a road surface, the drive wheel tends to have an excessive amount of slip on the road surface, failing to effectively accelerate the vehicle. Since the drive force that can be produced by the drive wheel is maximum when the slip ratio of the drive wheel is at an optimum value, it is proposed to lower or limit the rotating speed of the drive wheel such that the slip ratio or slip speed of the drive wheel is held at the optimum value. An example of an anti-slip control device for lowering the speed of the drive wheel as indicated above is disclosed in Laid-open Publication No. 62-32231 of Japanese Patent Application No. 60-170301 filed in 1985 in the name of the assignee of the present application. Such an anti-slip control device may use means for reducing an output torque of a drive source of the vehicle, and/or means for applying a brake to the drive wheel, in order to lower the rotating speed of the drive wheel.
Although an anti-slip control device as described above may improve the accelerating capability of the vehicle, a known arrangement of the anti-slip control device may not be completely satisfactory in attaining its function, where the vehicle is started on an uphill road having a low friction coefficient, for example, on a snow-covered uphill road. The vehicle cannot be smoothly started on the uphill road even with the anti-slip control device being properly operated.